1. Field of the Invention
The present invention relates to an under-water propulsion and/or steering device for a vessel which can be mounted underneath a submerged part of a vessel. Such a device includes a propeller (such as a a controllable pitch propeller), an assembly which mounts the propeller and which is rotatably connected to the vessel, and a means for mounting and dismounting the propeller assembly in a submerged condition.
The term vessel is intended to include any type of a floating structure on which the invention might be used, such as pontoons; floating members for carrying equipment for offshore activities, i.e., such as members where it is of importance to keep the vessel in a given position; and floating members where it must be possible to perform repair and maintenance work on the propulsion and/or steering device assembly without docking the vessel.
2. Description of Prior Art
Several means have been proposed for mounting and dismounting a propulsion and/or steering device on a vessel in submerged condition. A major difficulty has been to maintain an effective sealing of the propeller assembly and the inside of the vessel during mounting and dismounting of the assembly. To maintain continuous sealing of both the vessel and the propeller assembly, it has previously i.a. been proposed to make the means for transfer of rotational power to the assembly as a hollow trunk which surrounds the means for transfer of drive power to the propeller, these means being rotatably mounted in a sleeve which is to carry the assembly on the vessel. In these proposed systems the necessary sealing means is positioned at the end of an intermediate sleeve provided between the trunk of the propulsion and/or steering device and the sleeve, the trunk being adapted to be moved axially relatively to the intermediate sleeve so as to obtain the desired sealing during all the steps of the mounting and dismounting of the propeller assembly.
The relative axial movement of the trunk and the intermediate sleeve have been effected by means of manually-controlled exterior jacks serving to cause vertical movement of the assembly. However, these jack systems tend to be complicated and require manual work which, at least partly, has to be done by divers.